Smoking is the primary cause of lung cancer in US adults, and also an important cause of mortality from other conditions. Onset of smoking occurs during adolescence. Research provides extensive documentation of social influence effects on initiation, especially influence of parents and peers. We began studying the impact of movie smoking on early adolescent smoking behavior nine years ago in a sample of over 5000 Northern New England adolescents, and have continued the research with a longitudinal sample of over 6500 nationally representative US adolescents. We demonstrated and confirmed a cross-sectional association between exposure to movie smoking and adolescent smoking initiation and, among never smokers, endorsement of more positive expectancies and higher levels of susceptibility to smoking. We have followed up never-smokers in each cohort 1-2 years later, showing that baseline exposure to movie smoking predicted onset of smoking in the future, emphasizing controlling for confounding, and including up to 21 covariates in the most recent study. In this competing renewal application, covering the 5-year period beginning May 2007, we propose to shift our emphasis to understanding the process for the observed association. Continuing to follow our national sample of adolescents who were 10-14 years at baseline, we will test mediation and moderation (race and social risk) hypotheses with respect to smoking initiation. Proposed mediators include smoking risk prototypes, and coping expectancies. Additionally, we will model pathways to tobacco dependence as a function of ongoing exposure to movie smoking, examining multiple smoking dependence constructs: frequency/quantity measures, loss of autonomy, and perception of self as a smoker. To accomplish these goals, we will follow our longitudinal cohort biannually for 3 more waves (waves 5-7), until the group is 18 to 22 years of age. The sample will be enriched with African-American adolescents, to better study a group that appears in early adolescence to be resistant to the movie smoking effect on behavior. This study provides an unsurpassed opportunity to further investigate the mechanisms underlying the effect of exposure to movie smoking on smoking behavior in adolescents and young adults. Because U.S. movies are marketed and distributed all over the world, this research could have far-reaching public health implications for adolescents everywhere.